Device and method for filtering video images

Abstract: A device for filtering video images, of the type which comprises first and second circuit portions (3,4), each having first (PFy),(PFuv) and second (CFy),(CFuv) input terminals respectively adapted to receive digitalized luminance (Y) and chrominance (U,V) components of a television signal, and an output terminal coinciding with an output terminal of the device. The first and second circuit portions (3,4) further comprise first (5), second (6) and third (8) filters, cascade coupled to one another, and a fourth filter (9), respectively. The first (5), second (6) and third (8) filters incorporate computational circuit means which use a logic of the fuzzy type to process the digitalized luminance component (Y). The fourth filter (9) comprises, on the other hand, computational circuit means which process the digitalized chrominance components (U,V) based upon a parameter (knr) supplied from the second filter (6).

Description: This invention relates in general to devices for use in video applications, and specifically to a device for filtering video images, in particular TV pictures, using fuzzy logic. The invention is also concerned with a method for filtering video images, in particular TV pictures, using fuzzy logic. In particular, the invention relates to a device and corresponding method for filtering a video signal having a luminance component and a chrominance component, the device comprising a luminance processing circuit having an input that receives the luminance component of the video signal and a first output that provides a luminance output signal. The invention further relates to a system for filtering a video image that includes a luminance component and a chrominance component, comprising: an analog to digital converter block (ADC) that receives the luminance and chrominance components and digitizes them to produce digitized luminance and chrominance components; a first memory (FMp) for a preceding image field having at least first and second input terminals and at least first and second output terminals; a second memory (FMc) for a current image field, the second memory being connected to the analog-to-digital converter to receive the digitized luminance (Y) and chrominance (U,V) components, and having first and second output terminals; a digital-to-analog converter block (DAC) having first and second input terminals and first and second output terminals, corresponding to output terminals of the system (20); and a video signal filtering device (1) operated to a logic of the fuzzy type having input terminals connected to the output terminals of the first (FMp) and the second (FMc) memory and output terminals connected to the input terminals of the digital-to-analog converter block (DAC). As is well known, the attainment of improved quality in TV receiver images is tied, on the one side, to the possibility of reducing the noise which accompanies the television signal, and on the other side, to the reduced bandwidth of said signal. Noise, being an inherent feature of any telecommunications systems or television signal broadcasting networks, can be reduced by different filtering methods. The method of choice will be dependent on the characteristics of the type of noise to be filtered. For example, in order to filter out impulsive noise, median filters are employed, while recursive filters are used to filter out noise of the gaussian type. Both filtering methods achieve good results at an acceptable cost-to-performance ratio. Although performing advantageously from several aspects, such techniques still cannot provide good filtering capabilities in an adaptive way. As mentioned above, another problem which affects the quality of TV pictures is represented by the narrow bandwidth of the television signal. It should not be overlooked that the television signal is a three-dimensional signal which has two spatial dimensions, horizontal and vertical, and a third dimension, temporal, which allows the motion images to be displayed. The term "image field" will be used hereinafter to mean a set of lines forming a TV picture within one and the same time interval. The narrow bandwidth problem should be handled with reference to the three dimensions of the signal. In the prior art, an improvement could be achieved in the spatial resolution of the TV picture by a spatial filtering which adds a peak signal to the original television signal. On the other hand, an improvement was achieved in time resolution by means of interpolation algorithms. In either case, the circuit architectures that improve the TV picture resolution should provide a spatial or space/time filtering of the signal. The filtering provided by taking account of just the spatial information is carried out using so-called "intra-field" interpolation algorithms, i.e. algorithms which utilize information present in one and the same image field. Those algorithms which utilize information present in two consecutive image fields, thereby revealing the presence of motion (space/time filtering), are called "inter-field" algorithms. Time resolution can also be improved by doubling the frequency of the image field through a scanning rate converter. Alternatively, time resolution can be improved by doubling the line frequency of an image field. In all cases, it is common practice to employ low-pass filters, whether it is noise or the TV signal that needs to be filtered. In this way, however, the outline of the imaged objects will be blurred or attenuated, which can only be remedied by the added use of expensive directional filters. Recursive low-pass filters can even attenuate the high temporal frequencies related to the motion contents of an image sequence. These filters, therefore, should perform such that no filtering action is applied while motion is being detected. In such cases, the possibility of associating a motion detector with the filter architecture would be a desirable feature. Considering indeed a so-called pixel from a static region of the TV picture, it can be reproduced without filtering so as to leave the display resolution unaffected. But with a pixel which belongs to a motion region of the picture, what is to be displayed is instead the interpolated value of that pixel. Improved quality of a TV picture is also related to image contrast and luminance. In fact, it is desirable in many cases to increase the contrast and tune the luminance of an image due to a greater variation in the image brilliance with respect to the sensitivity of the means that acquires or stores it. It is on this account that details which are present in highly brilliant or very dark areas of the image are inadequately brought out. It should be emphasized that contrast is associated with details, whereas luminance conveys brilliance information. Two main approaches have been used in the prior art to increase contrast and tune luminance. A first approach is based on image definition expressed as the product of an illumination component and a reflectance component. By using a filtering of the homomorphic type, it becomes possible to reduce the illumination component, which is responsible for most of the change in brilliance, and simultaneously increase the reflectance component, which contains detail information. The second approach is based on the use of a dual-channel filter which, through non-linear characteristics, produces a large increase in contrast where brilliance reduction is high. It should be noted that the mean value of the illumination component represents locally the low spatial frequency component of the image, whereas contrast represents the high spatial frequency component. Consequently, contrast can be obtained as the difference between the image and the averaged value of the illumination component. Good results can only be achieved, by either the first or the second approach, on a narrow range of images, while the variety of the images involved in a TV representation is quite large. It is indeed for this reason that filters having highly adaptive modes should be provided. Several researchers having proposed using fuzzy filters in image processing. Alattar, "A Probabilistic Filter For Eliminating Temporal Noise In Time-Varying Image Sequences," 1992 IEEE International Symposium On Circuits And Systems, vol. 3, 1992, pp. 1491-1494; Taguchi et al., Fuzzy Filters For Image Smoothing," Proccedings SPIE - Nonlinear Image Processing V, 7-9 February 1994, vol. 2180, pp. 332-339; Arakawa et al., " Proposal of Median-Type Fuzzy Filter And Its Optimum Design," Electronics and Communications in Japan, Part 3, Vol. 76, No. 7, 1993. These prior art fuzzy filters do not deal with color images and do not suggest employing fuzzy filters for chrominance components of image signals. The underlying technical problem of this invention is to provide a device for filtering video images, and a method therefor, which by using a logic known from the technical literature as Fuzzy Logic, is adaptive, in the sense that it is capable of effectively filtering images beset with problems of noise reduction, space/time resolution, and wide brilliance variation. In this way, the image quality can be significantly improved. The technical problem is solved by a device as indicated above and defined in the characterizing parts of Claims 1, 14 and 18. In the drawings: Figure 1 is a diagram illustrating schematically a device according to the invention; Figure 2 is a diagram showing schematically a so-called working window of the device in Figure 1; Figure 3 is a fragmentary schematic diagram showing a detail of the device in Figure 1; and Figure 4 shows schematically a TV apparatus incorporating the inventive device. With reference to the drawing figures, generally and schematically shown at 1 is a device for filtering video images, in particular TV pictures, using fuzzy logic. It should be noted that the TV signal is three-dimensional and has an interlaced format. The signal has, therefore, three components: a component Y of the luminance signal and two more components, U and V, of the chrominance signal. With reference to Figure 4, the device 1 is incorporated to a television apparatus 20 comprising an analog-to-digital converter block ADC which has first and second input terminals corresponding to input terminals of the apparatus 20 and being adapted to receive luminance Y and chrominance U, V components, respectively, and first and second output terminals. Said apparatus 20 further comprises a first memory FMp and second memory FMc, respectively for the preceding image field and the current image field, each said memory having first and second input terminals and first and second output terminals. More particularly, the first and second input terminals of the second memory FMc are connected to the output terminals of the analog-to-digital converter block ADC. The output terminals of the first FMp and the second FMc memory are instead connected to input terminals of the device 1, specifically to an interface circuit 2 to be described. Also with reference to Figure 4, the apparatus 20 further includes a clock signal block 21, effective to generate appropriate clock signals Ckw, Ckr and connected to both memories FMp and FMc, as well as to the analog-to-digital converter block and the device 1. Lastly, the apparatus 20 comprises a digital-to-analog converter block DAC which has first and second input terminals connected to output terminals of the device 1, and first and second output terminals corresponding to output terminals of the apparatus 20. As shown in Figure 1, the device 1 is provided with at least four input terminals adapted to receive digital signals CFy, CFuv, PFy and PFuv. In particular, the digital signals CFy and CFuv relate to a current image field and are sampled luminance/chrominance signals from FMc, while the digital signals PFy and PFuv are corresponding digital signals of a preceding image field and supplied from Fmp. With reference to Figure 1, the device 1 is shown to comprise an interface circuit 2 effective to permit operation of the device 1 with both a 4:1:1 format and a 4:2:2 format of the components Y, U and V. The circuit 2 is provided with first, second, third and fourth input terminals, which correspond to the input terminals of the device 1, and with first, second, third and fourth output terminals. The device 1 also comprises a first and a second circuit portion, being designated 3 and 4 and respectively adapted to process the luminance component Y and the chrominance components U and V. Reference will be made hereinafter to the first circuit portion 3, which acts on the luminance component Y. It should be noted that this component contains information about the image brilliance, that is about the grey shade portion of the image. It can be seen in Figure 1 that the first circuit portion 3 comprises a first line memory LM1, having an input terminal and an output terminal, and a first filter 5, having first, second and third input terminals as well as first, second and third output terminals. Specifically, the input terminal of the first line memory LM1 is connected to a first circuit node A which is, in turn, connected to the first output terminal of the interface circuit 2, while the output terminal of said memory is connected to the first input terminal of the first filter 5. The second and third input terminals of the filter are instead connected to the first circuit node A and the second output terminal of the interface circuit 2. The first filter 5 operates in accordance with the inventive method and, using fuzzy logic signal processing techniques, effects a reduction in the impulsive noise which is present in the luminance component Y of the television signal. More specifically, this filter acts on a working window or image window which is shown in Figure 2 and obtained by suitably delaying the digital signals PFy and CFy. This window includes nine pixels. The pixels included in the first and the last line of the window belong to a preceding image field, whereas the digital signal X, on which the window is centered, belongs to the current image field and forms, therefore, the digital signal to be processed. On these signals, the first filter 5 performs so-called inference operations, through fuzzy hardware known per se and incorporated to the filter. It should be emphasized that the inferential operations are basically configured as IF-THEN rules, with at least one initial or fore preposition and at least one consequent implication. The first circuit portion 3 further comprises a second filter 6 connected in cascade with the first filter 5 and having first, second and third output terminals. In accordance with the method of this invention, and using fuzzy logic signal processing techniques, this second filter 6 both effects a reduction in gaussian noise and a scanning rate conversion of the luminance component Y. More particularly, the second filter 6 acts on the same working window as shown in Figure 2 and carries out, on the digital signals included in said window and obtained from the impulsive noise filtering step, appropriate inference operations through fuzzy hardware incorporated thereto and known per se. This filter outputs digital signals, respectively designated NRyout and SRCyout. The digital signal NRyout represents the signal obtained by the fuzzy step of filtering out the gaussian noise, while the digital signal SRCyout represents the signal obtained by the scan rate conversion step using fuzzy logic. Further, it can be seen in Figure 1 that the first circuit portion 3 includes a second line memory LM3 having an input terminal and an output terminal, and a first format converter circuit 7 having first and second input terminals and an output terminal. Specifically, the input terminal of the second line memory LM3 is connected to a second circuit node B, being in turn connected to the second output terminal of the second filter 6, while the output terminal of said memory is connected to the first input terminal of the first format converter circuit 7. The second input terminal of the first format converter circuit 7 is instead connected to the second circuit node B. This circuit, a viable implementation whereof has been shown in Figure 3, is adapted to effect a vertical format conversion of the suitably delayed digital signal SRCyout. Before describing the structure of the circuit 7, it should be pointed out that the device 1 can provide different magnifications of the image being processed. In particular, this device can provide a magnification of 12.5% or 25% of the image being processed. In either cases, however, to obtain a magnified image which would retain a correct proportion to its dimensions, a so-called vertical interpolation must be performed. This is performed in order to increase the number of the vertical lines which make up the magnified image compared to the original image. The interpolation algorithm used is given by the following formula: Yvfc = h1 * CurrLine + h2 * PrevLine where, Yvfc is the interpolated digital signal, and h1 and h2 are two parameters which take predetermined sets of values so as to keep the magnified image to the interlaced format. The sets of values taken by the parameters h1 and h2 vary with the magnification factor selected. The format converter circuit shown in Figure 3 is adapted to implement the formula (1) above. It comprises a storage element M, such as a read-only memory, for storing the sets of values taken by the parameters h1 and h2, and a periodic storage address generator G which is connected to said storage element M. Also in Figure 1, it can be seen that the first circuit portion 3 further comprises a third LM5 and a fourth LM6 line memory, each having an input terminal and an output terminal, and a third filter 8 provided with first, second, third and fourth input terminals as well as with an output terminal which forms a first output terminal Yout of the device 1. To be precise, the input terminals of the line memories LM5 and LM6 are connected to a third circuit node C, in turn connected to the first output terminal of the first format converter circuit 7, and to a fourth circuit node D, connected to the output terminal of the third line memory LM5. The first and second input terminals of the third filter 8 are connected to the third C and fourth D circuit nodes, while the third and fourth input terminals of said filter are connected to the output terminal of the fourth line memory LM6 and to a fifth circuit node E. The latter is connected to the first output terminal of the second filter 6 and to the first input terminal of the first memory FMp for the preceding image field. The third filter 8 is a dual channel filter adapted to perform, on the low-pass and the high-pass components of the luminance component Y, respectively a reduction in brilliance and an increase in contrast. More particularly, the filter 8 will carry out, respectively on the low-pass component and the high-pass component, a first and a second fuzzy process using conventional fuzzy hardware contained in the filter. As mentioned above, the device 1 also comprises a second circuit portion 4 intended for processing the chrominance components U and V. With reference to Figure 1, this second circuit portion 6 is shown to comprise a first delay block T1 having first and second input terminals which are connected to the third and fourth output terminals of the interface circuit 2, and first and second output terminals. Said block introduces a suitable time delay in the chrominance components U and V, so as to compensate for the delay already present in the luminance component Y as a result of the impulsive noise filtering step carried out by the first filter 5. The second circuit portion 4 further comprises a fifth line memory LM2 which has an input terminal and an output terminal, and a fourth filter 9 which has first, second, third and fourth input terminals and a second output terminal. To be specific, the input terminal of the fifth line memory LM2 is connected to a sixth circuit node F which is in turn connected to the first output terminal of the delay block T1, while the output terminal of said memory is connected to the first input terminal of the fourth filter 9. The second and third input terminals of the filter are instead connected to the sixth circuit node F and the second output terminal of the delay block T1. In addition, the fourth input terminal of the filter 9 is connected to the third output terminal of the second filter 6, while the output terminal of said filter 9 is connected to the second input terminal of the first memory FMp for the preceding image field. This fourth filter 9 both effects a reduction in gaussian noise and a scanning rate conversion on the chrominance components U and V of the television signal. The filter 9 processes the digital signals PFuv and CFuv, as suitably delayed, to produce a working or image window which has the same structure as that shown in Figure 2 for the luminance component Y. In particular, the fourth filter 9 performs appropriate operations on said signals, based on a parameter knr supplied from the second filter 6, through conventional computational circuit means incorporated thereto. The filter 9 will output digital signals, respectively designated NRuvout and SRCuvout. The digital signal NRuvout represents the resultant signal from the gaussian noise filtering step, and the digital signal SRCuvout represents the resultant signal from the scan rate conversion step. Also shown in Figure 1 is that the second circuit portion 4 further comprises a sixth line memory LM4, having an input terminal and an output terminal, and a second format converter circuit 10, having first and second input terminals and an output terminal. More particularly, the input terminal of the sixth line memory LM4 is connected to a seventh circuit node H being in turn connected to the second output terminal of the fourth filter 9, while the output terminal of said memory is connected to the first input terminal of the second format converter circuit 10. The second input terminal of the second format converter circuit 10 is connected to the seventh circuit node H. This circuit is effective to perform, on the suitably delayed signal SRCuvout, a vertical format conversion in accordance with the method previously described in connection with the first format converter circuit 7. The second circuit portion 4 then comprises a seventh line memory LM7, connected between the output terminal of the second format converter circuit 10 and an input terminal of a second delay block T2. Said block is also provided with an output terminal UVout, which forms a second output terminal for the device 1. The block T2 is effective to suitably delay the chrominance components U and V in order to compensate for the delay caused in the luminance component Y by the filtering steps carried out by the third filter 8. Finally, the device 1 comprises a control circuit C, shown in Figure 1, intended to control the internal synchronization of the device 1. The filtering method of this invention will now be described with reference, in particular, to an initial state whereby the digital signals of a current image field and a preceding image field are presented at the input of the interface circuit 2. As mentioned above, the method and device of this invention allow both the impulsive noise and gaussian noise present in the television signal to be reduced. The reduction in impulsive noise is only performed on the luminance component Y by the first filter 5. This filter, by utilizing the fuzzy logic inference operations carried out on the digital signal included in the working window shown in Figure 2, can determine whether the pixel X whereat the window is centered does contain noise. Based on this determination, the output from the first filter 5 will act as a soft switch, between the original digital signal and the output of a conventional median filter. The reduction in gaussian noise is performed by the second filter 6. It should be noted that the last-mentioned noise is correlated in space much more than in time. Thus, the pixels belonging to the preceding image field are used to filter the pixel from the current image field, according to the following formula: Ynr = knr * (Pi + Pj)/2 + (1 - knr) * X where: Ynr is the filtered digital signal; knr is 0 when the digital signal is moving and 1 when the digital signal is stationary; Pi and Pj are pixels along the direction with the greatest amount of correlation, in order to improve the filter performance in relation to edge attenuation. Now, the second filter 6 can, by using the fuzzy logic inferential operations, detect the movement as well as the edge of the video image. The fuzzy process output is a value of knr within the range of {0,1}. The formula (2) effects a soft switch between an approach wherein a movement or non-movement is processed along the direction of greatest correlation. It matters to emphasize that the parameter knr is also used to reduce gaussian noise present in the chrominance components U and V. In this case, due to the bandwidth of the television signal associated with the chrominance components, no directional filtering is carried out, and only the vertical direction is taken into consideration. The scan conversion will now be discussed. In relation to scan conversion, a procedure closely resembling that of the formula (2) above can be followed to determine the pixel to be interpolated. In fact, if the signal is stationary, the second filter 6 would output the current pixel, or alternatively, the averaged value along an edge. Therefore: Ysrc = ksrc * (Pi + Pj)/2 + (1 - ksrc) * X where: ksrc is 1 when the digital signal is moving, or 0 when the signal is stationary. Since: ksrc = 1 - knr the formula (3) can be rewritten as follows: Ysrc = knr * X + (1 - knr) * (Pi + Pj)/2 It will be more convenient to substitute the output Ynr obtained from the noise reduction for the original pixel X, so that the interpolation is carried out on noise-free pixels. Thus, the following relation is obtained: Ysrc = knr * Ynr + (1 - knr) * (Pi + Pj)/2 For the chrominance component, the procedure is much the same as the previous ones. In particular, the following formulae are used: UVnr = knr * (P2uv + P5uv)/2 + (1 - knr) * Xuv This formula applies to the noise reduction step, while the following applies to interpolation: UVsrc = knr * UVnr + (1 - knr) * (P2uv + P5uv)/2 where: P2uv and P5uv are pixels along the vertical direction. Furthermore, the device 1 can effect, on the components Y, U and V of the television signal, a vertical format conversion in accordance with the method described above. By means of the third filter 8, said device will also effect, respectively on the low-pass Ylp and the high-pass Yhp components, a decrease in brilliance and corresponding increase in contrast, using the following method. The filter estimates the mean brilliance values associated with the image and an image window obtained by suitably delaying the digital signals input thereto. Based on these values, the filter 8 will effect a decrease in brilliance on the component Ylp, using a first fuzzy procedure. Based on this decrease, it will effect an increase in contrast on the component Yhp, using a second fuzzy procedure. In conclusion, the device of this invention, by utilizing fuzzy logic signal processing methods, does solve the technical problem and significantly improves the quality of the TV picture.

Claims: A device for filtering a video signal having a luminance component and a chrominance component, the device comprising a luminance processing circuit (3) having an input that receives the luminance component of the video signal and a first output (Yout) that provides a luminance output signal, characterized in that the luminance processing circuit (3) also includes a fuzzy logic filter (6) performing inferential operations according to fuzzy logic signal processing techniques on said luminance component (Y) in order to produce a reduction in gaussian noise and a scan rate conversion by interpolation of said luminance component; said fuzzy logic filter (6) providing on a second output a fuzzy logic signal (knr) within the range {0, 1} indicative of whether an image defined by the video signal is moving or is stationary and in that the device includes a chrominance processing circuit (4), having a first input that receives the chrominance components (U, V) of the video signal and a second input coupled to said second output of the luminance processing circuit (3), including a fuzzy logic chrominance filter (9) performing inferential operations according to fuzzy logic signal processing techniques on said chrominance components (U, V) in order to produce a reduction in gaussian noise and a scan rate conversion by interpolation of said chrominance components using the value of said fuzzy logic signal (knr) as a multiplication factor of pixel values of a working window of the fuzzy logic chrominance filter (9). A device according to Claim 1, wherein the luminance component is digitized and the luminance processing circuit further includes a fuzzy logic hardware filter (5) adapted to perform, on the digitized luminance component (Y), inference operations effectively producing a reduction in impulsive noise of the luminance component. A device according to Claim 1, wherein the luminance component is digitized and the luminance processing circuit (3) includes a dual channel filter (8) acting on low-pass and high-pass components of the digitized luminance component (Y). A device according to Claim 3, wherein the dual-channel filter (8) is a fuzzy hardware processing suitably delayed low-pass and high-pass components of the digitized luminance component (Y), according to first and second fuzzy procedures to produce a reduction in brilliance and concurrently increased television signal contrast. A device according to Claim 1, wherein the chrominance component is digitized and suitably delayed before being input to said chrominance filter. A device according to Claim 3, wherein said fuzzy logic filter (6) has an output terminal connected to an input terminal of the dual-channel filter (8). A device according to Claim 2, wherein the luminance processing circuit includes a first line memory (LM1) is connected between the input of the luminance processing circuit and an input terminal of the fuzzy logic hardware filter (5). A device according to Claim 4, wherein the luminance processing circuit includes first and second line memories (LM5,LM6) having respective first and second output terminals, respectively connected to first and second input terminals of the dual-channel filter (8). A device according to Claim 5, wherein the chrominance processing circuit (4) includes a line memory (LM2) connected between the input terminal of the chrominance processing circuit (4) and an input terminal of the fuzzy logic chrominance filter (9). A device according to Claim 4, wherein said luminance processing circuit includes a format converter circuit (7) connected between said fuzzy logic filter (6) and said dual-channel filter (8) and arranged to process the suitably delayed digitized luminance component (Y) to produce a vertical format conversion of the luminance component (Y). A device according to Claim 10, wherein the luminance processing circuit includes a line memory (LM3) connected between an output terminal of the fuzzy logic filter (6) and an input terminal of the format converter circuit (7). A device according to Claim 5, wherein the chrominance processing circuit (4) comprises a format converter circuit (10) connected between the fuzzy logic chrominance filter (9) and the output of the chrominance processing circuit (4) and arranged to process the digitized chrominance component (U,V) to produce a vertical format conversion of the chrominance component (U, V). A device according to Claim 12, wherein the chrominance processing circuit (4) includes a first line memory (LM4) connected between an output terminal of the fuzzy logic chrominance filter (9) and an input terminal of the format converter circuit (10). A method for filtering a video signal having a luminance component (Y) and a chrominance component (U, V), the method comprising processing the luminance component through luminance fuzzy logic circuitry to produce a luminance output signal, characterized in that the step of processing the luminance component includes a fuzzy logic filtering phase performing inferential operations according to fuzzy logic signal processing techniques by a fuzzy logic filter (6) on said luminance component (Y) in order to produce a reduction in gaussian noise and a scan rate conversion by interpolation of said luminance component and a fuzzy logic signal (knr) within the range {0, 1} indicative of whether an image defined by the video signal is moving or is stationary and the method further includes processing the chrominance component through chrominance fuzzy logic circuitry including a fuzzy logic chrominance filter (9) performing inferential operations according to fuzzy logic signal processing techniques on said chrominance components (U, V) in order to produce a reduction in gaussian noise and a scan rate conversion by interpolation of said chrominance components using the value of said fuzzy logic signal (knr) as a multiplication factor of pixel values of a working window of the fuzzy logic chrominance filter (9). A method according to Claim 14, wherein an impulsive noise in the luminance component (Y) is reduced. A method according to Claim 14, wherein a brilliance reduction is performed on the luminance component (Y) and a concurrent contrast is increased. A method according to Claim 16, wherein an estimate of averaged brilliance values associated with a corresponding working window is made within a further fuzzy logic filter (8) operating according to fuzzy logic signal processing techniques. A system for filtering a video image and including a luminance component (Y) and a chrominance component, (U, V) comprising: an analog to digital converter block (ADC) that receives the luminance and chrominance components and digitizes them to produce digitized luminance and chrominance components; a first memory (FMp) for a preceding image field having at least first and second input terminals and at least first and second output terminals; a second memory (FMc) for a current image field, the second memory being connected to the analog-to-digital converter to receive the digitized luminance (Y) and chrominance (U,V) components, and having first and second output terminals; a digital-to-analog converter block (DAC) having first and second input terminals and first and second output terminals, corresponding to output terminals of the system (20); and a video signal filtering device (1) according to claim 1 and having input terminals connected to the output terminals of the first (FMp) and the second (FMc) memory and output terminals connected to the input terminals of the digital-to-analog converter block (DAC), said filtering device (1) being feedback-connected to the input terminals of the first memory (FMp) so that the filtered noise reduced components are supplied to the input terminals of the first memory (FMp).

Inventors: D ALTO VIVIANA, MANCUSO MASSIMO, POLUZZI RINALDO, RIZZOTTO GIANGUIDO, D'ALTO, VIVIANA, MANCUSO, MASSIMO, POLUZZI, RINALDO, RIZZOTTO, GIANGUIDO
Applicants: ST MICROELECTRONICS SRL, STMICROELECTRONICS S.R.L.
Application year: 1994
Main classification: H04N9
IPC codes: H04N5, H04N9, H03H17